Exemplary embodiments of the present invention relate to methods for detecting the trajectories of projectiles.
Soldiers in action in crisis regions are constantly at threat of being fired at by hand weapons from behind (e.g. by so-called snipers).
Methods are already known for deriving information regarding position and direction from which the shot is fired. These methods involve acoustic sensors that determine the position of the shooters from the muzzle blast. Such acoustic sensors are disadvantageous because they require multiple spatially distributed and networked supporting positions (microphones). Moreover, such acoustic systems can easily be disturbed by ambient noise. Accordingly, acoustic sensors cannot be used on travelling or flying platforms or can only be used thereon in a limited manner.
Optical methods are also known for attempting to discover the optical sights of sharpshooter weapons. The application area of these systems is strictly limited because the firing of other hand weapons cannot be detected. These systems are also significantly adversely affected in their efficiency by ambient influences such as light sources or dust.
German patent document DE 10 2006 006 983 A1 discloses a method for detecting the trajectory and direction of motion of projectiles by means of a coherent pulse Doppler radar. The measurement of distance to a detected object involves using the transition time of the echo pulse, while the projectile speed is advantageously determined by means of the Doppler frequency shift in the echo signal.
Another method for detecting the trajectory and direction of motion of projectiles is disclosed in the publication Allen, M. R.; Stoughton, R. B.; A Low Cost Radar Concept for Bullet Direction Finding Proceedings of the 1996 IEEE National Radar Conference, 13-16 May 1996, pp 202-207.
German patent document DE 40 12 247 A1 discloses a sensor system, with which the azimuth angle, elevation angle, radial distance and radial speed of a target are measured.
German patent document DE 40 08 395 A1 discloses a monopulse radar for determining the azimuth, elevation and distance of a projectile.
Exemplary embodiments of the present invention provide a method that can reliably and universally detect the trajectory and direction of motion of projectiles.
In order to determine the trajectory parameters of projectiles (e.g. rifle bullets), it is assumed that they travel in a straight line and the speed in the detection region is constant. These assumptions are permissible in a number of applications, in which it is a case of detecting the penetration of projectiles into a protection zone and the determination of the direction from which the shot originated. Only either the direction in the plane (azimuth) or in addition the elevation direction is of interest here.
A continuous wave Doppler radar with the capability for indicating a bearing can be advantageously used as a sensor in the present invention. The angular resolution can be achieved either with a plurality of receiving antennas or sending/receiving antennas with a directional effect or with digital beam forming (DBF). The analysis of the Doppler signal enables the measurement of the radial speed components of the detected objects. The coverage of the radar sensor can be divided into individual angular segments, which are detected with spatially distributed individual and/or multiple sensors (sending/receiving modules).
Because projectiles typically have a higher speed than all other reflecting objects, the extraction of relevant signals can be accomplished by spectral discrimination in the form of high pass filtering. This also applies if the sensor is disposed on a moving platform (with a ground speed of up to about 300 km/h). This results in effective clutter suppression.